What is Gravity Transmission Fluid Change?
3 Answers
Gravity transmission fluid change involves loosening the drain plug of the transmission oil pan to allow the fluid inside the transmission to drain out by gravity, and then adding new transmission fluid through the fill port. Below are the related details: 1. Advantages: The gravity method is simple and quick to perform. It can replace about half to two-thirds of the transmission fluid. The cost of this method is relatively low. 2. Disadvantages: The transmission fluid is not completely replaced, especially in transmissions where a significant amount of fluid remains inside. Some transmissions cannot have their filters replaced, which can lead to premature deterioration of the new fluid and failure to meet the specified service interval.
I've been repairing cars for over a decade and frequently perform gravity transmission fluid changes. Simply put, it's about letting the transmission fluid drain naturally to replace it with new fluid, similar to changing water in a fish tank. We first lift the car, unscrew the drain plug, and the old fluid flows into a bucket. After about ten minutes, when it's mostly drained, we tighten the plug and pour new fluid through the fill hole. The advantages are that it's time-saving and cost-effective, requiring no removal of the oil pan, and can be done in half an hour. However, there's a drawback: in automatic transmissions, the old fluid in the torque converter doesn't drain easily, leaving about 30% of old fluid behind. It's recommended to do this every 40,000 kilometers and not wait until the fluid turns black, as it better protects the transmission gears.
Last time I had the transmission fluid changed in my Corolla, the mechanic used the gravity drain method. After lifting the car and opening the drain plug, the fluid slowly trickled out like pouring soy sauce for quite a while. The mechanic said this is the most traditional fluid change method preferred by repair shops because it doesn't require special equipment. The fluid quantity must be precisely controlled according to the service manual specifications - overfilling can cause foaming and affect lubrication. I noticed much smoother gear shifting after the change, with a slight improvement in fuel economy too. However, the mechanic warned that if the transmission fluid is particularly dirty or has a burnt smell, there might be too much residual contamination, in which case removing the oil pan for a thorough cleaning should be considered.
